Solar photocatalytic degradation of methylene blue in carbon-doped TiO2 nanoparticles suspension

Carbon-doped TiO2 nanoparticles were prepared by sol–gel auto-combustion method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Brunauer–Emmett–Teller method (BET), UV–vis diffuses reflectance spectroscopy (DRS). UV–vis diffuse reflectance spectra showed that carbon-doped TiO2 exhibited obvious absorption in the visible light range. The visible light photocatalytic activity of carbon-doped TiO2 was ascribed to the presence of oxygen vacancy state between the valence and the conduction bands because of the formation of Ti3+ species in the as-synthesized carbon-doped TiO2. The sample calcined at 873 K showed the highest photocatalytic activity under solar irradiation. The effects of photocatalyst concentration, initial concentration of methylene blue, and pH value in aqueous solution were also presented.